This report presents selected findings from the second follow-up of the High School Longitudinal Study of 2009 (HSLS:09). HSLS:09 follows a nationally representative sample of students who were ninth-graders in fall 2009 from the beginning of high school into higher education and the workforce. Key research topics for HSLS:09 include secondary to postsecondary transition plans and the evolution of those plans; paths into and out of science, technology, engineering, and mathematics (STEM) studies and careers; and the relationships between students' school experiences (educational and social) and their academic, work, and life plans and paths. The second follow-up data collection was conducted from March 14, 2016, through January 31, 2017, approximately 3 years after high school graduation for most of the cohort. The data collected allow researchers to examine an array of young-adulthood outcomes among fall 2009 ninth-graders, including delayed high school completion, postsecondary enrollment, early postsecondary persistence and attainment, labor market experiences, family formation, and family financial support. This report highlights selected findings from the HSLS:09 second follow-up data with the goal of encouraging interested researchers to explore the data for their own analytic purposes.